Contractor: Aerosol Dynamics

Contract Number: ICAT 04-03

A water-based, micro-environmental condensation particle counter (ME-WCPC) has been developed to provide monitoring of particle number concentrations in ambient air and in occupied spaces. Reported here is the evaluation of this instrument under field conditions. Comparison is made to three types of butanol-based counters (TSI Models 3010, 3022, 3025) and to bench-scale water based counters (TSI Models 3785 and 3786). Ambient sampling was performed in the summer and winter in Riverside and in the winter in Berkeley, CA. Indoor measurements were made in one office and two homes, including one kitchen. At all locations the collocated ME-WCPCs agreed with each other, with the square of the correlation coefficient above 0.97 and slopes near 1. For particle number concentrations below 200,000 cm-3, measurements from the ME-WCPC are within 10% percent of those from the butanolbased TSI-3022, and higher than those from the dilution-corrected TSI-3010, consistent with the differences in the lower particle size limits cutpoints of the instruments (7 nm for the TSI-3022, 10 nm for the TSI-3010). Differences among all instruments are observed at concentrations above 200,000 cm-3. At all locations the ambient particle number concentrations exhibited a consistent diurnal pattern during each multi-week study period, with a dominant morning maximum and a secondary late afternoon maximum. In some cases, a third maximum is seen shortly after midnight. Indoor particle number concentrations appear to be dominated by indoor, rather than outdoor sources. Residential particle number concentrations associated with cooking activities were a factor of 10 or more higher than the highest levels observed outdoors.

For questions regarding this research project, including available data and progress status, contact:
Heather Choi
at (916) 322-3893